busybox: add '--show SCRIPT' option to display scripts

busybox: add '--show SCRIPT' option to display scripts

Add an option to allow the content of embedded scripts to be
displayed.  This includes applet scripts, custom scripts and the
.profile script.

function                                             old     new   delta
busybox_main                                         624     701     +77
find_script_by_name                                    -      24     +24
scripted_main                                         41      35      -6
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 1/1 up/down: 101/-6)             Total: 95 bytes

Signed-off-by: Ron Yorston <rmy@pobox.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>